Process for cleaning metal parts of combustion motors, especially parts made of aluminum or alloys of aluminum



Patented Jan. 7, 1941 PATENT omen PROCESS FOR CLEANING METAL PARTS OF COMBUSTION M 0 T O R S, ESPECIALLY PARTS MADE OF ALUMINUM OR ALLOYS OFAL Johan Piet Abrahams, Amsterdam, Netherlands,

assignor to Koninkli jke Zwavelzuurfabriekcn voorheen Ketjen N. V., Amsterdam, Netherlands No Drawing.

rial No. 293,488. 12, 1938 The application relates to a process for cleaning metal parts of combustion motors, especially parts made of aluminum or alloys of aluminum.

Parts of combustion motors, such as pistons, valves, cylinder heads, springs, etc., in the course of time are covered by a scale formed by combustion of lubricating oil, combustion of fuel, etc. This scale substantially consists of carbon, generally mixed with oil and decomposition products of oil and fuel.

This scale is harmful in various ways, as it causes increased 'wastage, overheating of .the motor, an irregular run of the motor, etc. Parts on which such scale has deposited musttherefore be cleaned at times. As however the scale sticks very fast to the metallic surface, its removal constitutes a diflicult problem.

Various processes have been tried out to remove this scale and among them the purely mechanical process is the most commonly applied. Under purely mechanical process there is to be understood besides scraping and grinding also the system of blasting with a sand jet, metal pulver or metal grains. This process has many disadvantages. On the one hand, the metal surface is worn off together with the black deposit; on the other hand it is often very difiicult to get access to various spots of the parts.

Ways and means have therefore since long been studied to remove the black scale from the metal parts by rinsing, soaking, etc. them by way of a chemical process. Here also however the general result has been that either the scale was insufflciently detached and dissolved or metal corrosion caused. Difiiculties more particularly occurredwith aluminum and aluminum alloys; a treatment with strong alkaline substances for instance was not possible.

Applicant has found that a very eflicient removal of the scale from parts of combustion motors can be easily obtained by treating these parts with concentrated sulphuric acid or oleum.

In this way a perfect removal of the scale is obtained, while corrosion of the metal parts does not take place at all or only to a degree to be neglected. line motors and of Diesel engines and, especially for such parts as are made of aluminum, duralumin and other aluminum alloys. The scale, in so far as it is not removed by the oleum or the sulphuric acid, anyhow is detached, so that it can be easily removed by brushing or rubbing.

To this end, the parts are immersed in a bath of sufficiently strong sulphuric acid or oleum. This This is true likewise for parts of gaso- Application September 5,1939, se-

In the Netherlands September 4' Claims. (Cl. 148-23) can be donewithout any pretreatment of the parts.

Care must be taken that the liquid comes into contact with the whole of the surface to be cleaned and that this. contact be not prevented by air-bubbles or the like. It therefore may be of advantage to cause the parts to move in the liquid.

Very good results are obtained with oleum containing 30% free S03, but also with oleum of a. higher or lower concentration. If however ordinary sulphuric acid of 100% or less is to be applied, it is recommendable to heat the liquid carefully in order to assure a complete removal of the scale.

In using a more diluted sulphuric acid, the process is no longer applicable to all metals, as these would be attacked. For iron parts, for instance, sulphuric acid in a concentration lower than 50 B. should not be used.

After the process with oleum or sulphuric acid, care should be taken that the adhering acid be removed or neutralized quickly, as otherwise dilution of the adhering acid would cause the metal to corrode.

In using oleum, rinsing with sulphuric acid of i for instance 60 B. can be practical. After the acid treatment, a rinsing with water takes place which eventually may be preceded by rinsing with a weak alkaline solution.

v In subsequently drying, care should be taken to prevent corrosion taking place under the influence of air or moisture. This may be carried out by immersing the parts in heated lubricating oil.

As the gases which emanate from oleum can be detrimental, especially so in motor workshops, and as they are objectionable to the'operating staff, it is recommendable to have them sucked off, which can be easily done for instance in .a horizontal direction.

.The following examples may serve as an elucidation:

1. A piston of a Wright cyclone aeroplane engine, which after 150 rotation hours was wholly covered with a black scale consisting chiefly of hard carbon and decomposed and dried oil, was

immersed in oleum containing 30% free $03.

At intervals the piston was caused to move through the oleum. After 10 hours, the piston was taken out of the oleum, rinsed first in sulphuric acid 60 B. and then in a 5% solution ofammonia in which it was brushed off. The black scale, in as far as it had not been dissolved in the oleum or been rinsed off, was removed 2 aaaepao without dii'lloulty in the solution of ammonia. as the scale now detached quite easily. The piston; which was made or an aluminum alloy, was perfectly bright alter the treatment and not in the least attacked. Finally, the piston was carefully rinsed with water and then dried.

2. A cast iron piston of an automobile four cycles engine complete with piston spring, bronze bearing and crank shaft was treated according to Example 1. It was found that only the Babbitt metal bearing was attacked. The piston was perfectly clean.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent is:

fuming sulphuric acid is heated.

4. A process as claimed in claim 1 and further comprising agitating the parts while in the fuming sulphuric acid bath.

JOH. P. ABRAHAMS. 

